linux-kernel - Re: [PATCH v3 1/2] cgroup: Show # of subsystem CSSes in cgroup.stat

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Message-ID: <76e70789-986a-44c2-bfdc-d636f425e5ae@redhat.com>
Date: Thu, 11 Jul 2024 13:39:38 -0400
From: Waiman Long <longman@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: Johannes Weiner <hannes@...xchg.org>, Zefan Li <lizefan.x@...edance.com>,
 Jonathan Corbet <corbet@....net>, cgroups@...r.kernel.org,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 Kamalesh Babulal <kamalesh.babulal@...cle.com>,
 Roman Gushchin <roman.gushchin@...ux.dev>
Subject: Re: [PATCH v3 1/2] cgroup: Show # of subsystem CSSes in cgroup.stat


On 7/11/24 13:18, Tejun Heo wrote:
> Hello,
>
> On Thu, Jul 11, 2024 at 10:05:22AM -0400, Waiman Long wrote:
>> Given the fact that for_each_css() iteration is filtering out csses that are
>> absent, the dying counts follow the same logic of skipping it if there is no
>> dying css. That also makes it easier to identify cgroups with dying
>> descendant csses as we don't need filter out entries with a 0 dying count.
>> It also makes the output less verbose and let user focus more on what are
>> significant.
>>
>> I do understand that it makes it inconsistent with the ways nr_descendants
>> and nr_dying_descendants are being handled as entries with 0 count are also
>> displayed. I can update the patch to display those entries with 0 dying
>> subsys count if other people also think that is the better way forward.
> I think it'd be better to have all the keys. There are some dynamic keys in
> stat files but those are mostly for things which can come and go (e.g. block
> and misc devices), so yeah, I think it'd be better to show all the keys even
> when they're zero.
Currently, I use the for_each_css() macro for iteration. If you mean 
displaying all the possible cgroup subsystems even if they are not 
enabled for the current cgroup, I will have to manually do the iteration.
>
> Also, I personally would much prefer if the same prefixes are collected
> together - ie. totals first and then dying. It's just a lot easier on the
> eyes that way.
>
> 	nr_subsys_cpu
> 	nr_subsys_memory
> 	nr_subsys_io
> 	...
> 	nr_dying_subsys_cpu
> 	nr_dying_subsys_memory
> 	nr_dying_subsys_io
> 	...

That is fine. I can group entries with the same prefix together.

Cheers,
Longman